Determination of the carbohydrate composition and the disulfide bond linkages of bovine lactoperoxidase by mass spectrometry

The extent and distribution of N-glycosylation and the nature of most of the disulfide bond linkages were determined for bovine lactoperoxidase through proteolytic and glycolytic digestions combined with matrix-assisted laser desorption/ionization mass spectrometric analysis. In addition, 98% of the primary sequence of the protein was confirmed. All five of the asparagines present in sequons were found to be glycosylated, predominantly by high mannose and complex structures. Six disulfide bonds were assigned, including Cys 32-Cys 45, Cys 146-Cys 156, Cys 150-Cys 174, Cys 254-Cys 265, Cys 473-Cys 530 and Cys 571-Cys 596.